The development of contact systems and interconnection systems for electronic devices integrated on a single substrate has been under development for some years. A multilevel system can be useful in providing a plurality of metal connection lines which may overlap each other without making electrical contact and also may provide for more than one layer of metal in the contact itself. A Schottky barrier type of contacting metal, for example platinum, is commonly used as a Schottky contact metal and subsequent to sintering to form platinum silicide at the surface of the semiconductor, is overlain with a layer of titanium tungsten to provide interdiffusion protection to the contact.
Another aspect of the metallization system is the requirement of reduced intermigration of the molecules at the contact surface which has the potential to cause "poisoning" of the active device or which can cause significant resistivity maintenance problems in the electrical conductor. For example, see U.S. Pat. No. 3,573,570 patented Apr. 6, 1971, which provides a good introduction to this technology as well as U.S. Pat. No. 3,754,168 patented Aug. 21, 1973, entitled Metal Contact and Interconnection System for Nonhermetic Enclosed Semiconductor Devices. Several of these problems as well as the problem of adherence to the surface are discussed in the U.S. Pat. No. 3,341,753 issued Sept. 12, 1967. The adherence problem of high conductivity metals to silicon oxide is noted.
Also, it has been taught that "Platinum and palladium themselves do not form oxide layers easily, and consequently their adhesion to thick layers of silicon dioxide is rather poor." Quoting from the text "Thin Films Interdiffusion and Reactions, edited by J. M. Poate, K. N. Tu and J. W. Mayer on p. 380. That chapter entitled, Silicide Formation, chapter 10, is incorporated herein by reference as are the above-identified U.S. patents.
Accordingly, it is an object of the present invention to provide a process for forming an adherent metallic film on an insulator while at the same time reducing interdiffusion problems and reducing the number of process steps required.
Another object of the present invention is to provide a process for forming an adherent platinum film on the surface of an insulator.
A yet further object of the present invention is to provide an adherent metallic film on the surface of a silicon oxide or a silicon nitride material.